It has been recognized that drinking cups and other nestable containers with superior properties, especially for the retention of hot beverages such as coffee, can be formed from expanded thermoplastic materials, the most popular of which has been proven to be expanded polystyrene. Some different types of containers and methods for producing them have been proposed, and some have been successful in the marketplace.
Some design criteria which have been sought to be achieved are the elimination of the postprinting of the containers after they have been fabricated, the capability of producing containers with different sidewall configurations, including convex and concave surfaces by the same methods with minimum alteration to the apparatus, and the elimination of waste materials during the production of cups.
Various efforts have been directed to the production of thermoplastic cups, such as the molding of a one-piece cup directly from expanded polystyrene beads in a steam chest, the formation of a two-piece cup from a crescent-shaped blank of expanded plastic material, e.g. U.S. Pat. No. 3,468,467, and the production of a one-piece seamless deep-drawn cup, as disclosed in U.S. Pat. No. 3,666,162.
Commonly assigned, copending Amberg et al. U.S. patent application Ser. No. 354,305, filed Apr. 25, 1973, now abandoned a continuation-in-part of application Ser. No. 211,259, filed Dec. 23, 1971, now U.S. Pat. No. 3,854,583 discloses a method and apparatus for forming a two-piece nestable cup. The apparatus of this application utilizes a continuously moving conveyor carrying a plurality of spaced mandrels having an outer configuration corresponding to the inner contour of the cup. A main conveyor moves the mandrels along a closed path where a series of operational steps are performed which function in timed sequenced interrelationship to form the cup. While this apparatus functions extremely well to produce the improved nestable cup at high production speeds, the need remains for a simplified and less costly method and apparatus.